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diff --git a/spec/ruby/core/enumerable/to_h_spec.rb b/spec/ruby/core/enumerable/to_h_spec.rb
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+++ b/spec/ruby/core/enumerable/to_h_spec.rb
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+require_relative '../../spec_helper'
+require_relative 'fixtures/classes'
+
+describe "Enumerable#to_h" do
+  it "converts empty enumerable to empty hash" do
+    enum = EnumerableSpecs::EachDefiner.new
+    enum.to_h.should == {}
+  end
+
+  it "converts yielded [key, value] pairs to a hash" do
+    enum = EnumerableSpecs::EachDefiner.new([:a, 1], [:b, 2])
+    enum.to_h.should == { a: 1, b: 2 }
+  end
+
+  it "uses the last value of a duplicated key" do
+    enum = EnumerableSpecs::EachDefiner.new([:a, 1], [:b, 2], [:a, 3])
+    enum.to_h.should == { a: 3, b: 2 }
+  end
+
+  it "calls #to_ary on contents" do
+    pair = mock('to_ary')
+    pair.should_receive(:to_ary).and_return([:b, 2])
+    enum = EnumerableSpecs::EachDefiner.new([:a, 1], pair)
+    enum.to_h.should == { a: 1, b: 2 }
+  end
+
+  it "forwards arguments to #each" do
+    enum = Object.new
+    def enum.each(*args)
+      yield(*args)
+      yield([:b, 2])
+    end
+    enum.extend Enumerable
+    enum.to_h(:a, 1).should == { a: 1, b: 2 }
+  end
+
+  it "raises TypeError if an element is not an array" do
+    enum = EnumerableSpecs::EachDefiner.new(:x)
+    -> { enum.to_h }.should.raise(TypeError)
+  end
+
+  it "raises ArgumentError if an element is not a [key, value] pair" do
+    enum = EnumerableSpecs::EachDefiner.new([:x])
+    -> { enum.to_h }.should.raise(ArgumentError)
+  end
+
+  context "with block" do
+    before do
+      @enum = EnumerableSpecs::EachDefiner.new(:a, :b)
+    end
+
+    it "converts [key, value] pairs returned by the block to a hash" do
+      @enum.to_h { |k| [k, k.to_s] }.should == { a: 'a', b: 'b' }
+    end
+
+    it "passes to a block each element as a single argument" do
+      enum_of_arrays = EnumerableSpecs::EachDefiner.new([:a, 1], [:b, 2])
+
+      ScratchPad.record []
+      enum_of_arrays.to_h { |*args| ScratchPad << args; [args[0], args[1]] }
+      ScratchPad.recorded.sort.should == [[[:a, 1]], [[:b, 2]]]
+    end
+
+    it "raises ArgumentError if block returns longer or shorter array" do
+      -> do
+        @enum.to_h { |k| [k, k.to_s, 1] }
+      end.should.raise(ArgumentError, /element has wrong array length/)
+
+      -> do
+        @enum.to_h { |k| [k] }
+      end.should.raise(ArgumentError, /element has wrong array length/)
+    end
+
+    it "raises TypeError if block returns something other than Array" do
+      -> do
+        @enum.to_h { |k| "not-array" }
+      end.should.raise(TypeError, /wrong element type String/)
+    end
+
+    it "coerces returned pair to Array with #to_ary" do
+      x = mock('x')
+      x.stub!(:to_ary).and_return([:b, 'b'])
+
+      @enum.to_h { |k| x }.should == { :b => 'b' }
+    end
+
+    it "does not coerce returned pair to Array with #to_a" do
+      x = mock('x')
+      x.stub!(:to_a).and_return([:b, 'b'])
+
+      -> do
+        @enum.to_h { |k| x }
+      end.should.raise(TypeError, /wrong element type MockObject/)
+    end
+  end
+end